Running on grub-trunk rev 4574.
Attempting to: PXE boot Grub to boot various OS over NFS. Need load_env/save_env to access env between boots on diskless systems.
Problem: save_env can only store to disk.
Workaround: Use (http) module as workaround and script my way out of it server side.

How to setup:
PXE boot blobs constructed by grub-mknetdir. No grub.cfg config file is in use. need tftp and http and working network.
How to reproduce:
PowerOn Client: will tftp core.0, some modules and *.lst files.

3/5 times result in "Double Free at 0x1ffd8b60".
1/5 times result in "Alloc magic is broken at 0x1ffd65d0".
1/5 times result in "error: connection timeout".

cat always dumps file output (expect in last case), so I suspect the double free bug lies in the termination/closure of the http connection/module.

The last error occur because http module always use src port 21550. If httpd has not yet terminated its socket, an ACK on the sequence number from last cycle is re-sent. This cause http module to time out as no valid SYN-ACK is received. I suggest randomizing the source port number.

Attached is a pcap file with two cycles. First cycle has resulted in a "Double free", second cycle resulted in the "connection timeout" case.